note:

Everything preceding the characters "IN;" is part of the XON/XOFF handshaking setup.

ESC Is the escape character

.I

Initiates the handshake mode (period "eye", not period "ell")

.N

Used to set up a trigger character

.I

Is setting up an Xoff threshold of 81 bytes and an Xon trigger character of 17.

.N

Is setting up the Xoff trigger character to be 19.

ISSUE: How Xon/Xoff works.

Solution

When using the Xon/Xoff handshake method, the plotter controls the data exchange sequence by signaling the computer when it has sufficient room in its I/O buffer for data and when it does not. The plotter uses buffer threshold indicators (an Xon trigger character and an Xoff trigger character) prevent buffer overflow.

Data enters the plotter's buffer faster than it can be processed, and the buffer starts to fill. When the data in the I/O buffer reaches the Xoff threshold level, the plotter sends the Xoff trigger character to the computer.

The plotter's buffer empties as data is processed. When the Xon threshold level is reached (approximately half the I/O buffer), the plotter sends the Xon trigger character to the computer, restarting the flow of data.

ISSUE: Setting up communication from DOS using the above statement.

Solution

This is not possible. DOS will always use hardware handshaking even if the Xon/Xoff statement is sent down to the plotter at the beginning of a plot file. Software must be involved when using Xon/Xoff handshaking.